/Engine/Source/Runtime/Core/Public/Containers/StringConv.h
Converts a Source string into UTF8 and stores it in Dest.
The number of bytes written to Dest, up to DestLen, or -1 if the entire Source string could did not fit in DestLen bytes.
template<typename SrcBufferType, std::enable_if_t< TIsCharEncodingCompatibleWith_V< SrcBufferType, [FromType](API\Runtime\Core\Containers\FTCHARToUTF8_Convert\FromType) >> *> static int32 Convert ( [IntendedToType](API\Runtime\Core\GenericPlatform\FGenericPlatformTypes\UTF8CHAR) * Dest, int32 DestLen, const SrcBufferType * Source, int32 SourceLen )